The present invention relates to a new and improved construction of a gripper head for looms working with removal of the filling threads from stationary bobbins or spools. The gripper head of the invention is of the type comprising a clamping gap formed by a stationary stop and a movable clamping tongue, the clamping gap serving for fixedly clamping a filling thread passing through the clamping gap essentially perpendicular to the central plane of the warp threads.
Gripper heads of this type are employed at gripper looms and serve the purpose of seizing the filling thread withdrawn from a stationary bobbin by means of a first gripper head, the so-called bringer-gripper or inserting carrier, introducing such seized filling thread approximately up to the center of the shed, at that location transferring the filling thread to a second gripper head, the so-called taker-gripper or withdrawing carrier, and then, finally drawing the filling thread through the second half of the shed. After departure of the taker-gripper out of the group of warp threads, the clamped filling thread is released. In order to drive the gripper heads, there are employed oscillating rigid rods which can be moved towards one another or flexible bands or tapes, at the front ends of which there are secured the gripper heads.
These gripper heads, which also are referred to by those skilled in this technology as clamping grippers, originally were designed such that the filling thread passed through the clamping gap and also the gripper head essentially parallel to the central plane of the warp threads. However, it has been found that such horizontal thread guiding in the gripper head is not capable of operating completely satisfactorily, either at the tape gripper looms and equally at the rod gripper looms. In particular, it is extremely difficult to maintain both of the gripper heads sufficiently stable in a direction perpendicular to the central plane of the warp threads such that the thread transfer at the center of the shed can always be accomplished in a positive manner.
It is for this reason that the gripper heads, during the past years, have been replaced by gripper heads of the previously mentioned type, wherein the filling thread passes through the clamping gap essentially in vertical direction. Gripper heads of this type are known to the art, for instance, from U.S. Pat. No. 4,062,382, granted Dec. 13, 1977, and U.S. Pat. No. 4,071,055, granted Jan. 31, 1978.
In practice, these gripper heads have indeed proven themselves to be superior to the first-mentioned prior art gripper heads, but nonetheless it can happen that notwithstanding a faultless functioning of the clamping tongue, the filling thread is suddenly released, particularly by the taker-gripper, and thus, is not completely inserted into the shed. This disturbance apparently is attributable to vibrations of the gripper head during the filling or weft insertion. These vibrations also can be transmitted to the clamping tongue, and, in unfavorable situations, can result in undesirable deflection thereof.